Method validation and residue analysis of methoxyfenozide and metaflumizone in Chinese broccoli under field conditions by liquid chromatography with tandem mass spectrometry

Environmental fate and safety analysis of methoxyfenozide application to control litchi and longan pests

Litchi and longan pests significantly affect crop yield and quality. Chemical prevention and control are very effective for production; therefore, it is crucial to study fate assessment and appropriate field efficacy before pesticide application on crops to appropriately assess the health and ecological risks linked with these agents. This study conducted Good Agricultural Practice (GAP) field trials and laboratory experiments to elucidate the dissipation, terminal residues, and efficacy of methoxyfenozide on litchi and longan in six locations throughout China. To detect methoxyfenozide residues on litchi and longan, a QuEChERS/UPLC-MS/MS-based method was designed. The initial methoxyfenozide levels in litchi and longan ranged from 2.21-2.86 to 0.83-0.95 mg kg-1 and indicated half-lives of 5.1-5.3 and 5.3-5.7 days, respectively. After 7 days of foliage treatment, the concentrations of terminal methoxyfenozide residue were 0.78-2.61 and 0.02-1.01 mg kg-1, which were less than the established maximum residue limit for methoxyfenozide in litchi and longan. The chronic (acceptable daily intake = 0.0055-0.0331%) dietary intake risk analysis for methoxyfenozide in longan and litchi indicated acceptable concentrations of terminal residue for the general population. Methoxyfenozide in litchi and longan was readily degraded in first-order kinetics models, the degradation rate on longan was higher than that on litchi, and their dietary risks were negligible to consumers. Two hundred forty grams per liter of methoxyfenozide suspension concentrate (SC) represents a highly efficacious insecticidal dose to control litchi and longan pests and indicates a significant application potential as it is rapidly degraded and linked with reduced post-treatment residue levels.

Dissipation pattern and safety assessment of fenazaquin and metaflumizone in butterbur (Petasites japonicus)

This study was conducted to investigate the residual behavior and safety assessment of fenazaquin and metaflumizone in butterbur. The samples were periodically harvested, extracted using QuEChERS method, and determined by LC-MS/MS. The linearity of matrix-matched calibration curve was ≥0.99 for both compounds. The average recoveries of fenazaquin and metaflumizone at two fortification levels (0.01 and 0.1 mg kg^-1) ranged from 86.6 to 97.2%. The relative standard deviation was <10%. After 7 days, the fenazaquin and metaflumizone initial residues in butterbur were dissipated to 79 and 78%, with the respective half-lives, 3.08 and 3.15 days. The proposed preharvest intervals (PHIs) for fenazaquin is recommended as twice treatment 14 days before harvest and metaflumizone twice treatment 7 days before harvest of butterbur. Risk assessment showed that the acceptable daily intake of fenazaquin and metaflumizone in butterbur was 0.004 and 0.029%, respectively. The respective theoretical maximum daily intakes of fenazaquin and metaflumizone were 58.74 and 15.15%, indicating negligible risk.

Residue Behavior of Methoxyfenozide and Pymetrozine in Chinese Cabbage and Their Health Risk Assessment

Methoxyfenozide and pymetrozine are used for pest control in the cultivation of Chinese cabbage. This has raised concerns in recent years due to health risks. Therefore, this study aimed to determine the residual concentrations of pesticides in the target crop and associated health risks. The dynamics and influence of environmental factors on the dissipation of methoxyfenozide and pymetrozine residues in Chinese cabbage were investigated. Analyses were performed using a modified QuEchERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) and an optimized high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The observed half-lives of methoxyfenozide and pymetrozine in cabbage samples ranged between two sampling seasons: in May−June, half-lives of methoxyfenozide and pymetrozine were 1.20 days and 1.89 days, respectively; during October−November, half-lives of methoxyfenozide and pymetrozine were 11.8 and 2.80 days, respectively. Meanwhile, a negative Spearman correlation was found between the residual concentrations and temperature (p < 0.01). This indicates that higher temperatures resulted in higher dissipation rates for methoxyfenozide and pymetrozine, suggesting that these pesticides degraded faster at higher temperatures. Additionally, higher pesticide residues in Chinese cabbage during low-temperature seasons resulted in higher risk quotients (RQ) (RQ > 1) for both analyzed compounds, which suggests that the effect of temperature on pesticide degradation needs to be considered as an essential factor while setting up the maximum residue limits (MRL).

Challenges in direct determination of Glyphosate and aminomethylphosphonic acid in water by LC-MS/MS at modified reverse phase columns: Effect of matrix interferences in fresh and hard water systems

This study validated two underivatized methods (M1 & M2) according to the Eurachem guidelines to analyze the herbicide Glyphosate and its major metabolite aminomethylphosphonic acid simultaneously by LC-MS/MS in both fresh and hard waters. Samples were analyzed directly after filtration through 0.22 μm syringe filters in M1, while samples were acidified with acetic acid before filtration in M2. Spike recoveries were greater than 80% for Glyphosate and aminomethylphosphonic acid in both methods. The LOQ was 0.5 μg L^-1 for M1, and 0.1 μg L^-1 for M2 by using matrix-matched calibrations. The linear regression coefficient of both methods was greater than 0.995. The expanded uncertainty was found to be less than 25% for both. Moreover, M1 has an additional mass spectral confirmation ability, and the column and the mobile phase used in M2 can be used to analyze the inert surfactant used in Glyphosate formulations, Polyethoxylated tallow amine. The accuracy of the developed methods was assured by participating in a proficiency testing program against M2, and conducting the t-test for results generated by both M1 and M2. Both methods, therefore, can be used to determine Glyphosate and aminomethylphosphonic acid content concurrently in fresh and hard waters. This article is protected by copyright. All rights reserved.